This project is focused on two aspects of development: chemotaxis and differentiation. As experimental organisms the cellular slime molds will be used. In one genus (Dictyostelium) we have already shown that cyclic AMP both acts as a cell attractant and induces stalk cell differentiation. In this study we wish to know the chemical nature of the chemotactic attractant of a closely related genus (Polysphondylium) (which does not respond to cyclic AMP) so that we might gain some insight into its chemotactic system and its relation to cyclic AMP chemotaxis. This includes an inquiry into the way the cells mange to inactivate attractants (including the inactivation of folic acid.) The differentiation part of the research will concentrate on the period where the first signs of differentiation appear. This involves the early control mechanisms which move the differentiation of cells towards stalk cells or spores, the mechanism of sorting out of these prestalk and prespore cells, and the chemical signalling mechanisms that control the proportions of stalk cells and spores.